1. Field of the Invention
The present invention relates to a cleaning device and an image forming apparatus having the cleaning device.
2. Description of the Related Art
In the image forming with use of the image forming apparatus such as a facsimile, a printer, or a copying machine, which employs electrophotography, steps of charging and exposing are performed by the rotation of a photosensitive drum, a developing step is then performed to form a toner image on a circumference of the photosensitive drum, subsequently, a transfer step follows thereto to transfer the toner image onto a record paper, and a discharging step is performed thereafter to discharge the circumference of the photosensitive drum.
In the image forming cycle, the residual toner left on the circumference of the photosensitive drum after the transfer step is performed is unnecessary for the discharging step and the charging step performed after the transfer step, and thus the image forming apparatus is provided with a cleaning device for performing a cleaning step between the transfer step and the discharging step, during which the residual toner on the circumference of the photosensitive drum is removed and collected.
As shown in FIG. 11, the cleaning device 7 comprises a device case 21 having a toner collecting space 22 opened to the circumference of the photosensitive drum 2; a blade holder 23 swingably supported by the device case 21 in the directions in which the blade holder approaches and leaves from the photosensitive drum 2 and extending to the opening of the toner collecting space 22; a blade 25 attached to the blade holder to cover together with the blade holder the opening of the toner collecting space 22 and to contact with the circumference of the photosensitive drum 2 when the blade holder swings in the direction approaching the photosensitive drum 2, so that the blade rakes up the toner left on the circumference of the photosensitive drum 2 toward the inside of the toner collecting space 22; and an elastic member 26 for applying a force to the blade holder in the direction in which the blade holder approaches the photosensitive drum so that the blade urgingly contacts onto the circumference of the photosensitive drum 2.
In order to prevent the leak of the toner collected in the toner collecting space 22 formed in the device case 21, the cleaning device is formed such that the opening of the toner collecting space 22 facing the circumference of the photosensitive drum 2 is covered with the blade holder 23, the blade 25, and the photosensitive drum 2, and the space between the outer face of the wall forming the toner collecting space 22 and the blade holder 23 is closed by an elastic seal member 28 attached to the wall of the toner collecting space 22 or the blade holder 23 to urgingly contact with the blade holder 23 or the wall of the toner collecting space 22.
The conventional elastic seal member 28 is formed such that contact faces 28m and 28n urgingly contacting with the blade holder 23 or the wall of the toner collecting space 22 are formed in planes, and contact faces 23m and 23n of the blade holder 23 and the wall of the toner collecting space 22 with which the contact faces of the elastic seal member 28 urgingly contact are also formed in planes so that the elastic seal member 28 can contact with the blade holder 23 or the wall of the toner collecting space 22 on a plane. In order to prevent the leak of the toner from the contacting face of the elastic seal member 28 and the blade holder 23 or the wall of the toner collecting space 22, the cleaning device 7 is installed in the body of the image forming apparatus 1 so that the blade holder 23 and the wall of the toner collecting space 22 urgingly contact with the elastic seal member 28 with a necessary pressure.
However, according to the above-mentioned structure of the conventional cleaning device, the entire plane contact faces 28m and 28n of the elastic seal member 28 urgingly contact with the plane contact face 23m or 23n of the blade holder 23 or the wall of the toner collecting space 22 in order to prevent the leak of the toner. With such a structure, when the cleaning device 7 is installed in the body of the image forming apparatus 1, the blade holder 23 and the blade 25 will shift from the predetermined position toward the photosensitive drum 2 (in the direction leaving from the elastic seal member). In addition, the elasticity of the elastic seal member 28 will decrease due to the yearly deterioration to shrink the elastic seal member. In accordance with the shrink of the elastic seal member, the contact face shifts backward from the desired contact position, which makes difficult to surely make contact the contact faces of the elastic seal member 28 and the blade holder 23 or the wall of the toner collecting space 22, with the result that the sealing performance of the contact faces will be deteriorated to leak the toner from the contacting section.
In order to solve the uncertainness of the contact, the contact pressure applied by the blade holder 23 or the wall of the toner collecting space 22 to the elastic seal member 28 is proposed to be increased. In this case, however, the elastic seal member 28 is strongly urged and compressed to generate a strong reaction force against the compression. The reaction force acts on the blade holder 23 to increase the pressure with which the blade 25 contacts with the circumference of the photosensitive drum 2. If the blade 25 contacts the circumference of the photosensitive drum 2 with more pressure than the necessary one, some problems such as the damage of the circumference of the photosensitive drum 2 may occur.
The object of the present invention is to provide a cleaning device having improved sealing performance on contact faces of the elastic seal member and the blade holder or the wall of the toner collecting space.
The other object of the present invention is to provide an image forming apparatus having the cleaning device mentioned above.
According to the first embodiment of the present invention, a cleaning device can be provided, which comprises a device case having a toner collecting space opened to a surface of a photosensitive drum; a blade holder swingably supported by the device case in directions in which the blade holder approaches and leaves from the photosensitive drum and extending to the opening of the toner collecting space; a blade attached to the blade holder in order to rake up toner left on the surface of the photosensitive drum toward inside of the toner collecting space; an urging member for applying a force to the blade holder in a direction in which the blade holder approaches the photosensitive drum so that the blade urgingly contacts onto the surface of the photosensitive drum; an elastic seal member attached to one of a wall forming the toner collecting space and the blade holder, between an outer face of the wall forming the toner collecting space and the blade holder facing the wall; and a protrusion attached to one of the blade holder and the wall forming the toner collecting space in order to prevent toner raked by the blade from leaking through a space between the blade holder and the wall of the toner collecting space.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.